I believe that UK can do better when not hampered by membership of EU
Oddly enough, I agree with that. But I also think the UK will not do as well when assisted by membership of the EU.   And I think the instances of the latter are far more numerous and beneficial than instances of the former.

Which is what all such legal agreements boil down to. You give up something in exchange for something you think is better. You give up some trade opportunities and other flexibility when you join the EU in expectation of greater benefits overall.

So it is perfectly fair and reasonable to ask what those benefits are and to want them to be in terms of financial and legal ramifications, with indications of uncertainities of course. As every business does when constructing its business plan for the next one, two or five years.